Impact shears are employed in the field of recycling for the fine grinding of material already coarsely ground and other related applications. The coarse grinding of recyclable objects takes place by a rotor shears or other methods. The known prior art impact shears have a motor driven rotor which carries a multiplicity of individual chopping blades. During operation the impact shears grind the desired material by the blades cooperating with a stationary blade held at the stator side.
Another known configuration of blades is to have the blades disposed in series, and extending over the entire length of the rotor. The blade of the stator is bolted in a blade holder. The blade holder can be set up in the radial direction with respect to the rotational axis of the rotor equipped with the chopping blades. This allows the user not only to set primarily the cutting gap, but also to be able to reset the cutting gap after a blade has been worn out. For this purpose the blade is bolted to the blade holder and consequently fixed in its position while the blade holder can be set via several setscrews relative to the stator in the above-described direction.
DE 195 14 951 C2 discloses a waste grinder in which the setting of the cutting gap takes place by utilization of an eccentric, which is simplified compared to the application of several setscrews.
In order to change the stationary blade, the blade must be removed from the blade holder and be replaced by a new one. In addition, the cutting gap between the new blade and the chopping blades on the rotor must be reset. In the case of grinding a very hard material, the wear and tear of the stationary blade is so high that it must be changed several times a week. This replacement of the blades is time consuming and during this time the impact shears are not operational.
In order to extend the changing intervals it is known to provide for the adjustability of the cutting gap, since the cutting gap resetting can be carried out in less time than a blade replacement. However, after a cutting gap resetting, cutting takes place with dull blades. Under some circumstances this can have a disadvantageous effect on the desired cutting result. Additionally, the danger exists that an overloaded blade can lead to the blocking of the rotor. For this purpose, in a chip breaker according to DE 43 28 506 C1 it is known to dispose the blade holder pivotably about an axis parallel to the rotational axis of the rotor at the upper end of a rotating shaft in order to provide an outside engagement position relative to the chopping blades of the rotor. This outside engagement position of the stator side blade relative to the chopping blades of the rotor takes place under formation of a coarse scale outlet as overload safety feature if a selectable cutting resistance has been exceeded. This ensures that such objects that cannot be ground can be immediately brought out of the cutting gap without the rotor needing to be stopped.
Building on this discussed prior art the present invention addresses the problem of providing an impact shears of the above described type in which the service life is increased and a blade change is facilitated.
This problem is solved according to the present invention wherein the blade holder carries at least two blades, usefully disposed at a mutually equal angular distance with respect to one another, or a blade configuration. The blade holder is rotatable about the axis extending parallel to the rotational axis of the rotor, such that each blade, or each blade configuration of the blade holder, can be brought into cutting position cooperating with the chopping blades of the rotor. In the cutting position one blade or one blade configuration cooperates with the chopping blades of the rotor and each blade or each blade configuration can be secured in position with respect to the cooperation with the chopping blades of the rotor.